Question 125180 in Android Studio Question posted in
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Android Studio – Android Studio error while using a function in setOnClickListener kotlin?

So i was testing my app with my phone that i’ve created in android studio and whenever i use the calc() function that i’ve done in setOnClickListener(), when i press the button my phone exits the app and i get errors:

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.fallingobject, PID: 20895
    java.lang.NumberFormatException: empty String
        at jdk.internal.math.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1842)
        at jdk.internal.math.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
        at java.lang.Double.parseDouble(Double.java:543)
        at com.example.fallingobject.MainActivity.onCreate$lambda$0(MainActivity.kt:32)
        at com.example.fallingobject.MainActivity.$r8$lambda$_3dgtv8ZNTl9g4zWX7J50i2eoew(Unknown Source:0)
        at com.example.fallingobject.MainActivity$$ExternalSyntheticLambda0.onClick(Unknown Source:4)
        at android.view.View.performClick(View.java:7498)
        at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:1202)
        at android.view.View.performClickInternal(View.java:7471)
        at android.view.View.access$3700(View.java:843)
        at android.view.View$PerformClick.run(View.java:29071)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loopOnce(Looper.java:233)
        at android.os.Looper.loop(Looper.java:344)
        at android.app.ActivityThread.main(ActivityThread.java:8205)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:589)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1071)

here is my code

MainActivity.kt:

package com.example.fallingobject

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import android.widget.Toast
import kotlin.math.sqrt


fun calc(vi: Double, height: Double): String {
    val a = 9.8

    val vf = sqrt((vi * vi) + 2 * a * height)
    val va = (vf + vi) / 2
    val t = height / va
    return t.toString()
}


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val calcBtn = findViewById<Button>(R.id.calcBtn)
        val vi = findViewById<EditText>(R.id.sIn).text.toString()
        val height = findViewById<EditText>(R.id.hIn).text.toString()
        calcBtn.setOnClickListener {
            val calculation = calc(vi.toDouble(), height.toDouble())
            //Toast.makeText(this@MainActivity, calculation, Toast.LENGTH_SHORT).show()
        }
    }
}

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#131313"
    tools:context=".MainActivity" >

    <EditText
        android:id="@+id/sIn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="100dp"
        android:layout_marginTop="100dp"
        android:layout_marginEnd="100dp"
        android:layout_marginBottom="55dp"
        android:backgroundTint="#BE40EC"
        android:ems="10"
        android:inputType="number"
        android:textColor="#673AB7"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@+id/hIn"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/hIn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="100dp"
        android:layout_marginTop="200dp"
        android:layout_marginEnd="100dp"
        android:layout_marginBottom="120dp"
        android:backgroundTint="#FFBE40EC"
        android:ems="10"
        android:inputType="number"
        android:textColor="#673AB7"
        app:layout_constraintBottom_toTopOf="@+id/calcBtn"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/calcBtn"
        android:layout_width="153dp"
        android:layout_height="56dp"
        android:layout_marginStart="100dp"
        android:layout_marginTop="364dp"
        android:layout_marginEnd="100dp"
        android:layout_marginBottom="80dp"
        android:text="Button"
        app:layout_constraintBottom_toTopOf="@+id/editTextNumber3"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/editTextNumber3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="100dp"
        android:layout_marginTop="500dp"
        android:layout_marginEnd="100dp"
        android:layout_marginBottom="186dp"
        android:backgroundTint="#FFBE40EC"
        android:ems="10"
        android:inputType="number"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="73dp"
        android:layout_height="33dp"
        android:layout_marginStart="100dp"
        android:layout_marginTop="50dp"
        android:layout_marginEnd="100dp"
        android:layout_marginBottom="31dp"
        android:text="Speed"
        android:textColor="#BE40EC"
        android:textSize="25sp"
        app:layout_constraintBottom_toTopOf="@+id/sIn"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="100dp"
        android:layout_marginTop="150dp"
        android:layout_marginEnd="100dp"
        android:layout_marginBottom="16dp"
        android:text="Height"
        android:textColor="#BE40EC"
        android:textSize="25sp"
        app:layout_constraintBottom_toTopOf="@+id/hIn"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

i tried commenting var calculation and everything related to calc() function and indeed it worked but i still need to use this function.

if this can help, i am using nougat 7.0

Tags:

2

Answers


  1. 0

    The number format is wrong, you can found the cause in exception description:

    java.lang.NumberFormatException: empty String

    The string is empty, so you have to search why it happened.

    ...
val vi = findViewById<EditText>(R.id.sIn).text.toString()
...
calcBtn.setOnClickListener {
   val calculation = calc(vi.toDouble(), height.toDouble())
}

    At start you get a value from text field and remember it in vi variable. At start text field’s value is empty string. In the click handler you try to convert this remembered empty string to double and got the error.

    You have to get value of text field in the click handler, something like this:

    val calcBtn = findViewById<Button>(R.id.calcBtn)
val vfield = findViewById<EditText>(R.id.sIn)
val hfield = findViewById<EditText>(R.id.hIn)
calcBtn.setOnClickListener {
    val vi = vfield.text.toString()
    val height = hfield.text.toString()
    val calculation = calc(vi.toDouble(), height.toDouble())            
}
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  2. 0

    It’s because your vi and/or height fields are empty. Try like this:

    calcBtn.setOnClickListener {
    if (vi.isNotEmpty() && height.isNotEmpty()) {
        val calculation = calc(vi.toDouble(), height.toDouble())
    }
}
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